As a vehicle body vibration control system, a system comprising a spring system provided with a control air spring, for controlling the internal pressure of the control air spring with the vibration acceleration of the vehicle body as a control input, is under development. This system has the advantage that a vehicle supporting spring other than the air spring holds a reference position of a suspension system. In view of the fact that the control input comprises the vibration acceleration of the vehicle body only, however, it is an important problem how to determine a compensator circuit for compensating the vibration acceleration and transferring it to a control device including an amplifier, a servo valve and the like. A compensator circuit presently suggested produces of a first order lead characteristic and a first order lag characteristic given as ##EQU1## or including also a second order lag characteristic, as ##EQU2## Kb: Transfer function of the compensator circuit K: Gain constant
T.sub.1 : Time constant of the first order lead characteristic PA0 T.sub.2 : Time constant of the first order lag characteristic PA0 S: Laplacian PA0 .omega..sub.n : Natural frequency of the second order lag characteristic PA0 .zeta.: Damping factor ratio of the second order lag characteristic
The response acceleration of the vehicle body in the vicinity of the natural frequency which is determined by the vehicle body support spring and the vehicle body mass can be kept at a low level, but the problem point is that the response acceleration of the vehicle body increases somewhat is the in upper and lower frequency ranges other than the frequencies about the natural frequency.